Publication Date:
2022-05-26
Description:
Also published as Journal of Physical Oceanography, Vol. 7, No. 3, May 1977, pp. 329-337
Description:
Estimates of horizontal derivatives of velocity made by differencing velocity measurements are used to
show that the observed velocity field due to low-frequency mesoscale motions during the preliminary MidOcean
Dynamics Experiment (MODE-0) field program is horizontally nondivergent within estimated
errors. The errors in horizontal derivatives of 0.15 X lQ-6 s-1 are too large for direct estimates of horizontal
divergence to be made accurately. The vorticity, however, can be estimated from these horizontal derivatives
with an error small compared with its magnitude. Over the measurement period of SO days, the advection
of planetary vorticity balances only one-half of the local change of vorticity so these observations
cannot be explained in terms of barotropic Rossby waves alone. There are indications that vortex stretching,
estimated from a linear heat balance, may balance the remaining local change of vorticity as expected
for baroclinic Rossby waves. Based on other measurements in this region; however, it is likely that the
horizontal advection of relative vorticity is also important in the vorticity balance. A positive, but not
significantly different from zero, correlation between estimates of relative vorticity and advection of planetary
vorticity suggests that the ens trophy of the observed velocity field is decreasing with time. In conjunction
with a similar result for the perturbation potential energy obtained in this region, this result supports
the view that the MODE region is a region of decay, rather than growth, of the low-frequency mesoscale
motions.
Description:
Prepared for the Office of Naval Research
under Contract N00014-66-C-0241; NR 083-004
and for the National Science Foundation, Office of the International Decade of Ocean
Exploration under Grant ID0?5-03962.
Keywords:
Ocean currents
;
Temperature measurements
;
Mid-Ocean Dynamics Experiment (MODE)
Repository Name:
Woods Hole Open Access Server
Type:
Technical Report
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